What is the space between the incoming stack pointer and (incoming stack pointer + getOffsetOfLocalArea) used for? getOffsetOfLocalArea is -$(WordSize) on x86. I was under the impression that it was used to store %rbp, but it seems %rbp is independently assigned a fixed frame index in X86FrameLowering::processFunctionBeforeCalleeSavedScan, and assigned its own slot in PEI::calculateFrameObjectOffsets. -- Sanjoy